your post makes me very sad personally.
One of TransforMap’s founding goal was to be a free mapping system independent from Google Maps, to be an alternative for commercial and non-free mapping systems.
The problem is that they require you to have all rights on the data you enter. So you cannot use any attribution-requiring, ore share-alike licensed data with Google, because they will not adhere to that license.
Therefore, syncing is (theoretically) only allowed if your data is essentially CC-0 or PD data (which have no usage restrictions).
There are two ways of entering data into GMaps:
Google My Maps - you create custom, independent maps that will not be indexed or display their POIs on maps.google.com
- You add POIs via Google Places (this is ‘the’ Google Maps)
Instead of Google My Maps, we would highly recommend to use Umap! Perfectly free alternative without being dependent on Google’s goodwill, and you will be able to choose your license.
The BIG problem with ‘main’ GMaps is currently, that is is very hard to change incorrect/outdated data put into “main” GMaps. From various experiences, they postpone change requests until the POI in question has a paid subscription for Google Ads :-/
Linking from/to is of course allowed. Is it possible to link from GMap entries to more than one other sites besides the POI’s homepage? If they don’t allow multiple links this makes very limited sense I guess…
I would personally urge you as a member of the alternative economy to NOT endorse unfree systems, and use free (as in Freedom!) alternatives.