You can download version 0.5.5 from this page - https://wordpress.org/plugins/wordpress-mu-domain-mapping/developers/.
That is the same as the development version. The development version was available for testing for months with no changes (ex. I removed the $wpdb->escape from sunrise.php in the development version 3+ years ago). Over that time I frequently responded to threads here indicating that the development version fixed warnings, etc.
In all of that time (3-4 years) no one reported back any issues with the development version in their threads. 18 months ago I released 0.5.5 & was inundated with 'I updated and it broke' threads. As a result, I released a new version which was a roll back to the previous version, So, the time saving effect of a new release would be substantially different that you would otherwise expect.
Secondly, WP core include arbitrary domain support which allows changing domains/URLs on any subsite. Domain mapping is only for legacy support. I have been working with WP for 10+ and domain mapping is not the first thing I have escorted into obsolescence.