You're missing a fundamental point. The bit where you say "follows GSL guidelines" (ignoring the "guidelines" phraseology - it's a license; there aren't any "guidelines" just instructions) specifically and directly does NOT cover web content.
The phrase "web content which folows the GSL" has no meaning. It's like saying "short and tall" or "fat and thin". Web content cannot folow the GSL, because the GSL very specifically does not apply to web content.
This gets very tangled, but here is how I am reading that:
Let's say you create a fictional baseball team, with fictional players, player's names, and player's backstories.
Let's say there is a license for use of the fictional team in fan created works, and that license (hereinafter called the
general license) contains three elements:
1. This license ("the general license") applies to all derivative works, except for web sites.
2. You may create derivative works so long as you do not alter the team makeup or backstories, and so long as your story is predominantly a story about a single baseball team.
3. If you use this license, you agree not to tell any stories about baseball teams, except as allowed by this license. If you do, you must cease all production and distribution of your licensed stories, and you have 90 days to destroy all retained copies of your stories which are subject to this license.
Let's say there is a fan kit that has photos of the players and a team logo, provided as media assets.
Let's say that the fan kit is provided with this specific
fan-site license:
1. You may use the media assets from the fan kit on your web page so long as the team name and logo are shown predominantly on the main page, and so long as you make no alterations to the media assets except to scale the images upwards or downwards by up to 50%.
2. To continue use of the fan kit, you must subject all material which you provide through the fan side to term (2) of the general license.
3. You agree also that any modifications to term (2) of the general license shall be considered to be made to the fan site license as well.
I don't have a way to explain it better, but I'm thinking that the fan site policy
embeds the terms of the general license. That seems to, in effect, create a wholly separate license which is free from the restriction in term (1) of the general license, while retaining specific elements of that license.