[ormaaj]

That is a contract, not a license. Or more accurately it's a contract with a copyright license embedded within its terms. This is an agreement with github to grant it an explicit license. Implied license is an implicit license. It may exist irrespective to any such agreements. Its implicit creation is an affirmative defense determined entirely by other factors and context.

The bar for this as a defense can be quite high, as it requires a clear intention to license the work as determined by a judge or jury.

Independent to the implied license doctrine there exists doctrine which governs mirroring, caching, and transferring of that content by 3rd parties and intermediaries. The combination of these is largely what makes sharing anything on the internet in lieu of licenses possible.

"user agreements" or "terms of use" are contracts that are essentially a redundant measure that gives parties like github much stronger protection, so that it doesn't have to rely upon any risky affirmative defense tactics that require meeting high legal thresholds.