Can I just showcase open-source project?

[MKebsi]

Anything posted in the Showcase gets reviewed. If your project doesn’t violate any of the community rules, you won’t get silenced! It is clearly stated:

About the Showcase category

Use this category to showcase any projects you have created using three.js. Showcases require moderator approval, so please be patient if your post doesn’t show up immediately, or feel free to message @moderators. Projects posted here will be considered for the three.js homepage, which is updated a couple of times a year.

You better contact moderators to resolve your issue.