From a business point of view, I understand the reasoning, but everyone wants everything for free ;-) I my concern is more that such a closed core/custom licen

From a business point of view, I understand the reasoning, but everyone wants everything for free ;-) I my concern is more that such a closed core/custom license doesn't bring with it the peace of mind that I usually associate with Free/OS software: that any work put into it, and any deployments (including future deployments) will be able to at least run on current code, regardless of licensing. And that was mostly an academic worry, until Oracle bought Sun, and demonstrated that companies would indeed do silly things to open software. Note that if it was Wallaroo that was "closed up", there'd be much more work and/or impossible to fork the system and continue using it. Sun with it's CDDL is also interesting for the problem wrt GPL incompatibility (which I think affects your license as well, (see: "Further Restrictions"). While I don't expect any of this code/system to run in the kernel, or inside some other system, like GCC - it is a (small) concern in terms of future use. It'll be interesting to see how this works out for you - I absolutely understand the need to monetize, and even if this is more of a "source available" license, than "Free Software" - it's still better than a completely closed system. But it'll never be distributed as part of eg: Debian/Main - like for example the jdk, or apache or spark is. I guess my main take-away is that this isn't "open source" but rather "source available" - because there's no way I can modify your software and sell/give/distribute it to someone and have them run it as and how they whish (Freedom zero). I don't mean this as criticism, but as an observation. [ed: On a more encouraging note, I know some big clients of Oracle/Solaris that were frustrated with the closed source offering, because there existed patches for problems on the open source OpenSolaris side for serious issues with big zfs deployments that took months to show up in the closed/supported offering from Oracle. So at least having a "transitive" license (if you have a license you can run community-improved code, not be bound to wait for upstream) is an improvement.] [ed2: Now, what happens when company X implements a similar license for compiler for language Z that is incorporated in Wallaroo (eg: APL/J, something new?) - but perhaps choose a different number of CPUs to trigger the need for a license? Could my system X-with-wallaroo require license fees from me to run at 12+ cpus, and from Wallaroo at 32+ cpus?). Just a thought.]