I'm not a lawyer, so take that into account when reading my reply :)
> Thanks. I must say, I prefer weak copylefts for my projects (MPLv2 with the incompatibility clause), so my concern isn't copyleft per se, but the virility of it.
I need to read up some more on MPLv2, but from what I've read now it looks like a license that could fit k6 as well.
> - Would a non-AGPLv3 open-source or source-available project using K6 be incompatible with AGPLv3 given they might "distribute" CI/CD along with their open-source or source-available code?
No, using k6 as a tool in CI/CD would not be a violation of AGPLv3 or trigger the virality of the license in regards to the non-AGPLv3 open source or source-available code base. Any k6 test scripts you write would also not need to be licensed under AGPLv3. Gitlab built an integration with k6 which could be seen as a data point in agreement with this view: https://docs.gitlab.com/ee/user/project/merge_requests/load_...
> - If a closed-source project publishes results from K6, are they now in violation of AGPLv3?
If we're talking about publishing results from testing of the closed-source project, then no, that would not be in violation. There's however an undefined gray area around clause 13 "Remote Network Interaction" in AGPLv3 in terms of what is allowed when for example offering a SaaS product based on an AGPLv3 licensed component such as k6. Clause 13 has not been tried in court afaik. It could seem that clause 13 would provide some protection for a business like ours from other companies building commercial solutions on top of k6, but from what I've been told by lawyers we shouldn't count on that, so we're not (anymore).
We have had many internal discussions on this topic, as well as with other companies and individuals in the open source space; whether to go the route of a source-available license, effectively restricting commercialization possibilities of k6 by other companies, or going the open core route and restrict what we release as open source. Everytime we've had this discussion internally we've come back to open source being the right choice for us, given the type of product we build and where we think we can capture value.
Beyond technology stack choices I'd say the biggest differences are that k6 is scriptable in JS whereas Tsung has scripting-like capabilities in XML, and that Tsung supports distributed execution of tests which k6 doesn't support yet (only in our SaaS product). Tsung also supports more protocols than k6 at the moment (eg. AMQP, MQTT, PostgreSQL etc.) but k6 supports HTTP/2 and gRPC which Tsung doesn't so depends on one's needs I suppose.
As I mentioned in reply to another comment, from a first look at MPLv2 it seems like it could be a good fit for k6 as well.
You said: > We chose MPLv2 specifically to address licensing concerns.
Is that something you've encountered while building Artillery? We've not met a lot of pushback from legal teams at companies using k6.