Good Morning All
A few notes here.
First, in relation to the DLS upload agreement. Keep in mind that we have sold payware packs (created by 3rd party groups, and with a somewhat less standardized royalty system) for approximately 6 years now, with freeware content being used as per the DLS agreement. All that the Trainz Content Creator Program system has done is implement a better method for us to communicate with the creators, and an easier way for them to submit the content. Apart from this, the same rules (and a similar agreement) have been in use for about 5 years now (at least, that's when I submitted my first payware pack through N3V).
As has been covered multiple times (both in this thread, and previously in other threads), the DLS EULA does allow us to distribute DLS content with DLC packs (in various forms - the TS2009 add-on packs were still DLC; just in a more manual package/system), as well as part of the built-in content set. This requirement has been there for the life of the Download Station, and the DLS upload agreement is relatively unchanged for this time from what I was able to tell.
In regards to locked assets. If it is marked as 'built-in' (this is what should be shown for DLS content that is packaged with built-in content, or with DLC packs), then it can be edited. However, as we have made changes to the .texture format, existing unofficial tools may not be able to read them. Since we don't officially support opening/editing of the '.texture' format (not has this ever been supported), we don't provide tools to do this. Like in previous cases, a 3rd party may be able to produce a tool to read/view these files.
If it's marked as 'payware', then it is not able to be edited. Unfortunately, some assets have been incorrectly marked as 'payware' in TANE, and we may look into this in future (it is relatively low on the to do list, compared to other tasks). Mostly this seems to have been caused by us needing to produce updates to the assets, and the updates not making it to the DLS before that build of Trainz was created. You can still view the config.txt file (and any scripts that aren't encrypted). The .texture files in these assets become encrypted, and as such cannot be opened/viewed with any tools.
If a creator needs to update one of their assets that is marked as 'payware', and needs a 'source' version to be able to include the fixes/repairs, then they should contact us to obtain the source version. As above, if the changes are only related to config.txt or script, then these will still be accessible.
Note, I did pass on this thread to our team for them to look at in relation to other points bought up, and will leave that to the rest of the team to respond to when they are able to.