Educause and Sakai - strong opponents of Blackboard's patent claims on the LMS and more aren't wholehearted about their support of Blackboard's patent pledge - although Blackboard has included in the pledge many named open source initiatives (Elgg being one of them), regardless of whether they incorporate proprietary elements in their applications, Blackboard has also reserved rights to assert its patents against other providers of such systems that are "bundled" with proprietary code. Is that wiggle room or what?
This bundling language could be construed in any number of ways - introducing "legal and technical complexity and uncertainty which will be inhibitive in this arena of development."
And that. after all, was Blackboatd's intent from the beginning. They were not after a patent - they were after scaring away the new development, scaring away institutions from pursuing open source actions - because maybe, just maybe, Blackboard would try to take them to task.
In fact EDUCAUSE and Sakai worked to gain a pledge that Blackboard would never take legal action for infringement against a college or university using another competing product. Blackboard could not agree for reasons related to its existing legal case.
Fear, sadly, is often more effective than the rule of law.