Check license compatibility upon extension install
When a new extension is installed it is not checked whether the extension license complies with the requirements of the TYPO3 CMS. By current understanding a TYPO3 CMS extension requires to be licensed under the GPL or LGPL at a version of 2 or later. This is not the case with all extensions. There are quite a lof of extensions swirring around which are not clearly licensed under the GPL, distributed by third-parties under unclear legal conditions and whatsoever.
Additional effort should be put into adding utility/service classes for determining the TYPO3 CMS extension compatibility upon installation and upgrade/update of an extension from TER or other sources. This could be accomplished by checking the "license" field of the composer.json file supplied with an extension and by adding a new "license" field to the ext_emconf.php file.
I do not know the current plans whether to drop or keep the ext_emconf.php in favour of a composer.json. But currently the "ext_emconf.php" is one (if not the only) "sign" which marks a directory in "typo3conf/ext/" as an official extension!