Okay, I have (a bit) more details for you. I got a copy of the bill so I could check the exact wording, I am not a lawyer, just a concerned citizen but I am sure many of you are curious to know so I am sharing it.

First, to understand how this law amendment was introduced, it's important to understand the original act, called the "TELECOMMUNICATIONS BUSINESS ACT" which is the main act regulating the sector. Article 50 of this act defines a list of prohibited acts by market participants, and the related Enforcement Decree prescribes a number of punitive measures the Korean Communication Commission is allowed to take against entities found in breach of Article 50 (the measures range from corrective orders to penalties).

Here is the original article:

   Article 50 (Prohibited Acts)(1) No telecommunications business operator may engage in any of the following conduct (hereinafter referred to as "prohibited acts") which undermine or are likely to undermine fair competition or users' interests, or allow other telecommunications business operators or third parties to engage in such conduct: <Amended by Act No. 13823, Jan. 27, 2016; Act No. 15858, Dec. 11, 2018> 1. Placing unfair or discriminatory conditions or restrictions on the provision of equipment, etc., joint utilization, joint use, interconnection or joint-use services, wholesale services, provision of information, etc.;

. . . ...and the list goes on, to end at number 8:

  8. Unfairly restricting measures to delete any software unessential to implementing functions of a communications terminal device or measures equivalent thereto; or installing and operating or suggesting any software that unfairly restricts the installation of other software.

Now what this amendment does is add the following three prohibited acts to the list:

Korean:

  9. 앱 마켓사업자가 모바일콘텐츠 등의 거래를 중개함에 있어 자기의 거래상의 지위를 부당하게 이용하여 모바일콘텐츠 등 제공사업자에게 특정한 결제방식을 강제하는 행위
  10. 앱 마켓사업자가 모바일콘텐츠 등의 심사를 부당하게 지연하는 행위
  11. 앱 마켓사업자가 앱 마켓에서 모바일콘텐츠 등을 부당하게 삭제하는 행위

English:

  9.  For app market operators, abusing their dominant position as intermediary in mobile contents transactions to force upon the mobile content providers the usage of a designated (specific) payment method 
  10.  For app market operators, unfairly and unduly delaying the review  of  mobile contents submitted to the marketplace [by mobile contents providers]
  11.   For app market operators , unfairly and unduly deleting mobile contents from the marketplace

Please note:

1) All translation is mine.

2) I am not a lawyer.

3) I am only sharing this because I learned so much from the HN community and because I've repeatedly seen requests for details about this law.

4) The bill(Korean): https://likms.assembly.go.kr/filegate/sender36?dummy=dummy&b...

Telecommunications Business Act, with its Enforcement Decree (English): https://elaw.klri.re.kr/eng_service/lawTwoView.do?hseq=50189