If you logged in with a GitHub account and starred their project, you would be entered into a contest for a chance to win some products (or gift cards) like Baskin Robbins, Starbucks, movie tickets, etc.
I translated it to English, and also looked at the images and I came to the same conclusion. From the images, it seems maybe they were giving away free products or gift cards if you starred the project.
My understanding (from Google Translating various posts) is that a company was trying to incentivise people starring the GitHub page (in an effort to justify the project internally?[1]). From the Facebook page (Google Translated):
> metatron discovery event
> Event period: 7/1 (Mon) - 7/20 (Sat)
> How to participate: Please comment on this post after capturing screen shot of STAR on metatron discovery in GitHub.
> Announcement of winners: 7/23 (Tue) (Individual will be contacted)
[1] 국내에서.. 특히 대기업내에서 이런 오픈소스 프로젝트가 유지될수 있을 것으로 생각하는 이는 거의 없을 것이라고 생각합니다. 이런 환경속에서 저희로써는 매년 매순간 이 프로젝트가 잘 될 수 있다고 증명해야했고, 그 중 하나가 star 의 개수였습니다. -> I do not think there will be many people in the domestic market that think that such open source projects can be maintained, especially in large corporations. In this environment, we had to prove every year that the project could work well, One of them was the number of stars. -- quote from a comment by kyungtaak, a contributor.
Without knowing the language, the images at least imply that they're giving away free stuff in exchange for people signing up on github and starring their repo.
Metatron discovery event prematurely closed .
We will send Starbucks gift cards through individual mail to those who participated in the event sequentially.
We will inform you about the early termination of the event below.
We apologize for any inconvenience this may have caused you.
As soon as we realized that the event could be interpreted as an event that could harm the open source ecosystem, we ended the event as soon as possible.
As an event coordinator, I would like to encourage our products to be more widely known to more developers, and I apologize for any inconvenience to the event without fully understanding the open source ecosystem.
We take heed of the developers' complaints on this issue, and we will take this mistake as a lesson to deepen our understanding of open source and contribute to the ecosystem. In addition, we will continue to support our members who are working hard to develop Metatron in the future so that we can communicate more sincerely with developers.