This is the contact editor (and only the editor) from the Android 2.1 sources.
I just fixed it to make it work with arbitrary contact sources (like CardDAV-Sync) and removed the dependencies on the internal API to make it work with Android 2.2 and later.
So all credits go to Google.
This editor is a replacement/alternative for your native editor and it's invoked in the same way. It will be started whenever you try to edit or create a contact (and you select "Contact Editor Free").
If you can edit all your contacts you may not have any benefits from this app. It is useful if you use some custom Sync-Adapter that does not feature its own editor (like CardDav-Sync) and your editor can not edit those contacts.
However some people reported it is useful if your phone's manufacturer removed the ability to edit custom labels.
Also, have a look at "Contact Editor Pro" an improved version of this editor. ( https://market.android.com/details?id=org.dmfs.android.contacteditorpp )
Get support and news via Twitter https://twitter.com/dmfs_org
This app can not edit or remove contacts from read-only sources like Facebook or Cloudtact! This is due to the definition of read-only!
Also, if you see a blank screen when editing contacts that are aggregated with a Facebook contact, try to remove and recreate your Facebook account. Facebook limits access from other apps which breaks the contacts API in a way. For further information see http://techcrunch.com/2011/02/22/google-android-facebook-contacts/
Note regarding Events:
There is a big problem with events in this editor (better: with Android). The Android SDK documentation states about the database column for the date: 'The event start date as the user entered it.' Unfortunately does every manufacturer have it's own opinion about the format. Some are happy with 'yyyy-mm-dd', my phone uses unix timestamps.
So if your phone doesn't accept the 'yyyy-mm-dd' format try entering a unix-timestamp ;-). Seriously, I think about removing this feature until I've found a proper solution. You can help by sending me mails with your phone model, os version and which formats work or don't work for you.
Btw: just writing a comment like "Doesn't work on..." won't help neither you nor me to get it running on your device. Please contact me if you have problems.
Please report bugs by sending me a mail stating what happened and what you did before it happened. Often the Market bug reports are not very helpful without additional informations.
* on some devices this app hangs when it is opened. If this happens to you, please send me an email!
* crashes in some very rare cases. I've no further information about those cases and I'm not able to reproduce them. Please send me an email with your phone model, your OS version and what kind of sync-adapters you have installed. Thanks!
--- new in 0.6.3.1 --
fix launcher label (was "edit contact" but should be "create contact")
--- new in 0.6.3 --
Add launcher icon that always starts with a new contact. This is meant as a workaround for HTC One users. HTC Sense doesn't invoke 3rd party editors when creating new contacts.