(Hoping that someone from Unity can chime in)
Reading the Submission Guidelines, specifically point 1.1.1, it seems that an MIT license should be allowed for a free asset:
"Submissions of free products that you, the submitter, have developed and are providing open sourced through other sites, will be allowed to include a EULA. As long as that content meets all other applicable requirements of this doc, is perpetually free and that EULA is compatible with our own. The compatible licenses that we mainly allow are MIT, BSD 3-Clause, and Apache. "
However my asset submission was rejected by the automatic testing with the following message:
“We cannot accept this package because it contains an independent license for your files. All packages on the Asset Store are protected by the “Asset Store End User License Agreement”. Other files or licenses that conflict with this End User License Agreement are not allowed within packages on the Asset Store.”
Any ideas on how to proceed with this?