I don't know what all features & fixes might be present in the updated version of that engine
As far as I remember, the newer versions of the code mainly contain the following two fixes:
- wrap-around movement
- corrected chain explosions
Both issues affect a number of currently unsolvable EMC levels.
Another (rare) problem that currently does not work right in the current native EM engine is the fake acid element.
but if it is simply not available due to license issues, it might as well not exist...
Theoretically, all existing versions of the code are "affected" by that issue. From my understanding of "license revocation" (and that of others with more legal knowledge than I have), revoking an open source license cannot be done retroactively, but only for new versions/revisions/releases of code released under some open source license. (Just think about potential license revocation regarding open source projects like the Linux kernel, the MySQL database, the Apache web server or whatever else open source software that comes to your mind -- but not for the next version (people would then fork the last "free" version of the software into a new open source project), but retroactively for all versions that were ever released.)
For that reason, I will continue treating source code that was once released under an open source license as still available under those license terms. Regarding the EM/EMC engine code, I have half a dozen of versions here that are newer than the version integrated into R'n'D (with the above mentioned features and fixes). Some of these versions have open source licenses that are compatible with the GPL that R'n'D is released under (like the 3-clause BSD license or a zlib style license), some have incompatible licenses (like the 4-clause BSD license). I will only use those compatible versions, of course.
It seems to me (out of whatever naivete) that implementing left-right wraparound, only, without anything else that might be missing, would be (A) fairly easy, and (B) fix something like 90% of EMC currently problematic EMC levels.
Yes, you may indeed be right. Please send patches!
For the last few years, due to those licensing annoyances, I haven't bothered to check if it could be done easily or not by myself...
(But I may change my mind and do the fix by myself one day, or just replace the current version of the EM/EMC engine with the last "license compatible" version of the code as described above.)
Is there a worry that doing that small step would re-ignite the code ownership controversy?
No.