The current Code-OSS packaging patches the package so that Code uses Microsoft's extensions marketplace, as seen in product_json.diff ([1]). The problem with that approach is that marketplace.visualstudio.com, as specified by its EULA, p. 1.b ([4]), can only be used by the Microsoft Visual Studio's family of products, and it's unclear whether custom builds, like Code-OSS is, are allowed to use it ([2][3]). This means users running Code are potentially breaking Microsoft's ToS.

There's an open package registry, Open VSX [5], that can be used as a possible replacement. The fixes to product.json needed to use Open VSX with Code-OSS have already been outlined by the VSCodium project, see [6].

[1]: https://github.com/archlinux/svntogit-community/blob/packages/code/trunk/product_json.diff
[2]: https://github.com/microsoft/vscode/issues/31168
[3]: https://github.com/microsoft/vscode/issues/31168#issuecomment-498803448
[4]: https://aka.ms/vsmarketplace-ToU
[5]: https://open-vsx.org/
[6]: https://github.com/VSCodium/vscodium/blob/master/DOCS.md#extensions-marketplace