[thatcks]

A CLA is a legal contract between two parties. An open source license is a general grant of additional permissions under copyright (and sometimes some additional promises regarding things like patents), provided that the person using those permissions (to make and distribute copies) adheres to certain requirements.

(I am the author of the linked-to article.)

[bmitc]

How is a software license not a legal contract? Everywhere I've seen treats it as such.

A normal CLA is just making things that are implicit when contributing code explicit. It is a clarifying statement and agreement on who maintains control. So if the complaint is that CLAs force you and your company or institution to be explicit when contributing code, then I'm not sure I understand the complaint.