Softwr

Automation Integration · head to head

Flowable vs Nebula

Flowable logo

Flowable

Automation Integration

Apache 2.0 BPMN, CMMN and DMN engine from the team that originally built Activiti

From
Free
Rated
-
Full reviewWebsite
Nebula logo

Nebula

Networking

Certificate based overlay network from Slack, with identity and firewall rules carried in the certificate

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Flowable the open source engine is genuinely usable but ships without the modelling studio, work application and admin console, so an open source deployment means building your own user interfaces before anyone can use it.; Nebula the open source project has no user interface, no enrolment workflow and no revocation service, so certificate issuing, distribution and expiry become scripts you write and then have to keep working.
  • They diverge on capability: Flowable covers BPMN 2.0 engine, Nebula covers Certificate carried identity.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Flowable and Nebula actually diverge.

Attributes where Flowable and Nebula differ
AttributeFlowableNebula
Pricing modelquoteOpen source, no licence fee
PlatformsLinux, Windows, Docker, Kubernetes, CloudLinux, macOS, Windows, iOS, Android, FreeBSD
CategoryAutomation IntegrationNetworking

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Flowable

  • BPMN 2.0 engine
  • CMMN case management
  • DMN decision tables
  • Spring Boot integration
  • Modelling studio
  • Task and case application
  • REST APIs
  • History and audit

Only in Nebula

  • Certificate carried identity
  • Group based host firewall
  • Lighthouse discovery
  • Noise protocol encryption
  • Unsafe routes
  • Managed option

What people use each for

The jobs each tool is most often brought in to do.

Flowable

  • An insurer automating claims handling where each case follows a different path and BPMN alone cannot express itnot Nebula
  • A bank embedding process orchestration inside an existing Spring Boot estate rather than buying a separate platformnot Nebula
  • A team leaving Activiti or jBPM that wants the same API family with active commercial maintenancenot Nebula
  • A regulated organisation needing complete process history and decision table audit trails for supervisorsnot Nebula

Nebula

  • Flattening a network across several clouds and datacentres without VPC peering or route tablesnot Flowable
  • Very large fleets where a central policy service on the connection path is unacceptablenot Flowable
  • Environments that already run an internal certificate authority and want the network to use itnot Flowable
  • Replacing per host iptables rules with policy written against roles that follow the hostnot Flowable

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Flowable

  • The open source engine is genuinely usable but ships without the modelling studio, work application and admin console, so an open source deployment means building your own user interfaces before anyone can use it.
  • It expects Java engineering capacity; teams looking for a business-user low-code automation tool will find the modelling and deployment cycle far too technical.
  • Enterprise pricing is not published and is quoted per deployment, leaving buyers without a benchmark against Camunda or IBM alternatives.
  • The Activiti fork left three engines with related APIs and overlapping documentation in circulation, and search results routinely return advice for the wrong one.
  • Flowable AG is a small Swiss company relative to its competitors, so the partner network, training market and pool of engineers with production experience are all limited outside Europe.

Nebula

  • The open source project has no user interface, no enrolment workflow and no revocation service, so certificate issuing, distribution and expiry become scripts you write and then have to keep working.
  • Revoking a compromised host means distributing a blocklist entry to every other host and reloading them, which is a fleet wide operation rather than a click, and easy to get wrong under pressure.
  • Changing a host group membership means reissuing and redeploying its certificate, so policy changes are a deployment rather than a configuration edit.
  • There is no identity provider integration or single sign on in the open source version, so it maps well to servers and badly to a fleet of user laptops.
  • NAT traversal is best effort and hosts behind symmetric NAT need a relay configured deliberately, so connectivity failures show up as intermittent rather than immediate and are awkward to diagnose.

Pricing, plan by plan

Flowable

Free
  • Flowable Open SourceFree
    • Apache 2.0 licensed BPMN, CMMN and DMN engines
    • Embeddable Java library or standalone apps
    • No modelling studio or enterprise applications
  • Flowable Enterprise$undefined/year
    • Modelling studio, work application and admin console
    • Connectors, forms and advanced identity management
    • Support with SLA and version maintenance

Nebula

Free
  • NebulaFree
    • Full functionality under the MIT licence
    • No host limit
    • You operate the certificate authority and lighthouses
  • Defined Networking$undefined/month
    • Hosted control plane and enrolment
    • Managed certificate lifecycle and revocation
    • Policy and DNS interface

Which should you pick?

Choose Flowable if

  • You need bpmn 2.0 engine.
  • You want to start without paying.
  • You work on Linux, Windows, Docker, Kubernetes, Cloud.
  • You also want cmmn case management.
Flowable review

Choose Nebula if

  • You need certificate carried identity.
  • You want to start without paying.
  • You work on Linux, macOS, Windows, iOS, Android, FreeBSD.
  • You also want group based host firewall.
Nebula review

Questions people ask

Is Flowable or Nebula better?
Neither clearly leads. Flowable starts at Free and Nebula at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Flowable or Nebula?
Flowable starts at Free and Nebula at Free.
Does Flowable or Nebula run on more platforms?
Flowable runs on Linux, Windows, Docker, Kubernetes, Cloud. Nebula runs on Linux, macOS, Windows, iOS, Android, FreeBSD.
Can I use Flowable for free?
Both have a free tier, so you can try either at no cost before committing.
What is Flowable best used for?
Flowable is most often used for an insurer automating claims handling where each case follows a different path and bpmn alone cannot express it, a bank embedding process orchestration inside an existing spring boot estate rather than buying a separate platform, a team leaving activiti or jbpm that wants the same api family with active commercial maintenance, a regulated organisation needing complete process history and decision table audit trails for supervisors. Of those, an insurer automating claims handling where each case follows a different path and bpmn alone cannot express it and a bank embedding process orchestration inside an existing spring boot estate rather than buying a separate platform are not what Nebula is typically brought in for.
What can Flowable do that Nebula cannot?
Flowable covers BPMN 2.0 engine, CMMN case management, DMN decision tables, Spring Boot integration. Nebula covers Certificate carried identity, Group based host firewall, Lighthouse discovery, Noise protocol encryption.

Answered from the vendors’ own pages

Flowable: Is Flowable open source?

Yes, the BPMN, CMMN and DMN engines are Apache 2.0. The modelling studio and enterprise applications are commercial.

Nebula: Does it use WireGuard?

No. Nebula predates the common WireGuard mesh tools and uses the Noise protocol framework with its own certificate format.

Flowable: How does it relate to Activiti and jBPM?

The same core developers built jBPM, then Activiti, then forked Activiti in 2016 to create Flowable.

Nebula: Can I run it without Defined Networking?

Yes, entirely. Defined Networking sells the control plane conveniences, not the network itself.

Flowable: What does Flowable Enterprise cost?

Nothing is published. It is quoted per deployment by the vendor.

Nebula: How do I revoke a host?

Add its certificate fingerprint to the blocklist in the configuration of the other hosts and reload them. There is no online revocation check.

Flowable: Why choose it over Camunda?

CMMN case management is a first-class engine, which matters when work is exception-driven rather than a fixed sequence.

Nebula: Is it a good fit for laptops?

Less so than the identity provider based tools. There is no single sign on, so every laptop needs a certificate issued and renewed by whatever process you build.

Share

Related pages

More on Flowable

More on Nebula

Keep looking

Other head to heads