Their "this is not specific personalised advice, consult your own lawyer" thoughts were:
1. The license does not specify revocable or irrevocable, but it would be likely a court would find it to be irrevocable because:
- other lanaguage in the license such as the perpetual term and the option to use later versions appears to anticipate it being non-revocable
- the zection on termination only provides for breach of contract and protects sublicenses of the terminated work from being terminated unless the sub licenses were also infringing. The fact that it provides some grounds for terminatioj but "we have a new license" isn't among them hurts their argument.
- There is mutual consideration and this is even spelled out in the contract as being consideration in terms of the derivative content being reciprocally licensed, plus the unspecified benefit to Wizards of having more complements to their product increasing its appeal. The licensee obviously gets the rights to use the covered content.
- The 23 year usage of OGL 1.0a may constitute reliance especially when combined with past clarifying public statements where Wizards official documents and then-active employees indicated it was intended to be non-revocable.
- Clauses in US law for copyright owners to terminate licenses require 35 yeara and do not affect sublicenses, so unlikely a court would assume a stricter unwritten standard of revocability than this
However, they also point out you can waive your rights to use content under 1.0a if you were to agree to 1.1, e.g. to get access to 6e content.
They also touch on the idea of if Wizards could use others OGL 1.0a licensed content under 1.1 which imposes lesser restrictions on wizards than 1.1. They're vaguer on this point, but imply probably not as its too much of a deviation from the previous license and raise the reliance part again