I agree that it would be better to not require JavaScripts. (But, I think it can be helpful to have mirrors on other services as well, for this and other reasons.)

However, there are some work arounds to some situations. Git could (presumably) still be used, if you have that (although you might not want the entire repository and only some files, so that is a possible issue with this). If you have a URL of a specific file that you can change "blob" to "raw" in the URL to access the raw file (this works on other services as well and is not specific to Gitlab). For commits, you can add ".patch" or ".diff" on the end of the URL (this also is not specific to Gitlab).