shadowoflameth
Adventurer
So you were publishing content? When you say you used the content, if that's meaning in your own unpaid, non-commercial gain, they don't care. They just want a cut of MONEY made from the content. If the 3rd party that you mention publishes derived content and is no longer licensed, they may be on a legal hook for some money. The only effect on you, the player or DM is that there will likely be less or no new 3rd party content going forward.Except there are sublicenses involved. For example, I used a fair amount of content from Matt Finich's Swords & Wizardry in my Majestic Fantasy RPG. At no time I used any material directly from the d20 SRD. But Matt did. Then there is the fact that the license has an explicit termination clause. And it mentions if the rights to the content are terminated all sub-licenses remain in force.
This could lead to an odd time-line where Matt Finch isn't allowed to publish or build on Swords & Wizardry but I am allowed to continue with the Majestic Fantasy RPG. Because my legal relationship for the Majestic Fantasy RPG is with Matt Finch not Wizards of the Coast.
The result is that the answer isn't as clear-cut as folks would like it to be.