The short answer is YES. The mobile apps (iPhone, Android, iPad, BlackBerry, etc) are all free to use forever.
Get It Done also offers a paid subscription version for a yearly fee of $39.  It provides access to the full set of functionality, which includes:
Basic FREESign Up Now  | Personal $39/YRGet Personal  | Team $29/MOGo Team  | 
- Single user
 - Syncing across multiple devices (phone, tablet, iOS, Android, Blackberry, Windows, Mac, and Web)
 - SSL data encryption (the same as online banks)
 - Daily backups of your data
 - Access your tasks offline
 - Add unlimited tasks
 - Free mobile apps
 - Email and Push notifications
 - Daily email reminders
 - 5 projects
 - 3 areas of responsibility
 - Attach web links to tasks
 - Share calendar
 - Repeating tasks
 - Assign tasks
 - 5 GB file uploads
 - Attach photos to tasks
 - Email tasks into the app
 - Email tasks out of the app
 - Export as a calendar
 - Schedule tasks for review
 - Archive projects
 - Dropbox support
 - Box support
 - Google Drive support
 - OneDrive support
 - Evernote support
 - Export to spreadsheet
 
  | - Single user
 - Syncing across multiple devices (phone, tablet, iOS, Android, Blackberry, Windows, Mac, and Web)
 - SSL data encryption (the same as online banks)
 - Daily backups of your data
 - Access your tasks offline
 - Add unlimited tasks
 - Free mobile apps
 - Email and Push notifications
 - Daily email reminders
 - Unlimited projects
 - Unlimited areas of responsibility
 - Attach web links to tasks
 - Share calendar
 - Repeating tasks
 - Assign tasks
 - 5 GB file uploads
 - Attach photos to tasks
 - Email tasks into the app
 - Email tasks out of the app
 - Export as a calendar
 - Schedule tasks for review
 - Archive projects
 - Dropbox support
 - Box support
 - Google Drive support
 - OneDrive support
 - Evernote support
 - Export to spreadsheet
 
  | - Add 35 People
 - Syncing across multiple devices (phone, tablet, iOS, Android, Blackberry, Windows, Mac, and Web)
 - SSL data encryption (the same as online banks)
 - Daily backups of your data
 - Access your tasks offline
 - Add unlimited tasks
 - Free mobile apps
 - Email and Push notifications
 - Daily email reminders
 - Unlimited projects
 - Unlimited areas of responsibility
 - Attach web links to tasks
 - Share calendar
 - Repeating tasks
 - Assign tasks
 - 5 GB file uploads
 - Attach photos to tasks
 - Email tasks into the app
 - Email tasks out of the app
 - Export as a calendar
 - Schedule tasks for review
 - Archive projects
 - Dropbox support
 - Box support
 - Google Drive support
 - OneDrive support
 - Evernote support
 - Export to spreadsheet
 
  | 
Upgrading is easy.  You won't be charged until after your free 30-day trial ends so give us a try worry-free.
See also How do I upgrade my account?