This title feels very misleading. It seems to center around a "harassment policy" rather than encouraging employees to contribute to open source or paying them to do so.
The policy was not created to shield the company - it is already covered by contracts and local law, this policy is made for the benefit of the employee to know what help and support is available.
And no, participation does not require a policy - except for those groups that worry about potential harassment - and these groups are drastically underrepresented in OS.