Here's a comprehensive list of all changes. Replace "drupal" with "backdrop" (or case-equivalent) where expected:
The ~250 functions from https://gist.github.com/quicksketch/7077150 all wrapped individually, including class methods.
No replacements provided for private functions.
The "drupal_" prefix on all of these are just dropped, since they universally are not needed and are non-public anyway. They'll also be converted to config before release.
drupal_css_cache_files => css_cache_files
drupal_stale_file_threshold => stale_file_threshold
drupal_js_version_query_string => js_version_query_string
drupal_js_cache_files => js_cache_files
drupal_private_key => private_key
drupal_weight_select_max => weight_select_max
Below aliased directly to BACKDROP_ equivelents.*
Below manually redefined because their files are not loaded early enough.
For testing only and not public, so it's not wrapped.
drupal_test_info => backdrop_test_info
Classes and Interfaces:
All wrapped with compatibility mode.
All wrapped in compatibility mode.
Using drupal_add_library() with drupal.* works with compatibility mode.
drupal.ajax => backdrop.ajax
drupal.batch => backdrop.batch