Normally, anything without a license is legally considered All Rights Reserved, so a license seals the deal and makes it public domain. There aren't many open source licenses for hardware, so I'd base off the GPLv2 and modify it to be hardware related.
Some changes if you do that:
Make distribution include the card itself, in the event that somebody sells a tweaked model. This would ensure they're being fair and sharing their modified schematics.
(maybe?) a clause that makes the vendor link to upstream, or the fork they're basing off. This would naturally leave a link trail going all the way to your original.
Normally, anything without a license is legally considered All Rights Reserved, so a license seals the deal and makes it public domain. There aren't many open source licenses for hardware, so I'd base off the GPLv2 and modify it to be hardware related.
Some changes if you do that:
Make distribution include the card itself, in the event that somebody sells a tweaked model. This would ensure they're being fair and sharing their modified schematics.
(maybe?) a clause that makes the vendor link to upstream, or the fork they're basing off. This would naturally leave a link trail going all the way to your original.