Tesla's way of opening up patents is interesting. Hopefully someone more knowledgeable on the topic can chime in, but my understanding is that Tesla's just saying they won't initiate a lawsuit if they believe you're using their patent in "good faith". Tesla's lawyer's clarification made their "good faith" restriction much more restrictive:
A party is “acting in good faith” for so long as such party and its related or affiliated companies have not:
- asserted, helped others assert, or had a financial stake in any assertion of
(i) any patent or other intellectual property right against Tesla or
(ii) any patent right against a third party for its use of technologies
relating to electric vehicles or related equipment;
- challenged, helped others challenge,
or had a financial stake in any challenge to any Tesla patent; or
- marketed or sold any knock-off product (e.g., a product created by imitating
or copying the design or appearance of a Tesla product or which suggests an
association with or endorsement by Tesla)
or provided any material assistance to another party doing so.
That's a little bit different than, say, Toyota, which offered to licenses out their patents royalty free with no strings attached and even offer consulting on how to use them for a fee. There's some guarantees there (or can be negotiated) that the tech/goodwill won't disappear on a whim.